Studies are being conducted on rats with neurogenic hypertension induced by sinoaortic denervation. Characteristicaaly the hypertension is of moderate severity and labile. Plasma dopamine beta hydroxylase, DBH, activity was shown to be elevated in these rats and current studies will compare DBH activity with plasma norepinephrine, NE and epinephrine, E, to ascertain whether the catecholamines vary in the same direction as DBH and/or correlate with blood pressure. A sensitive radioenzymatic - TLC method of assay is used for NE and E determinations. Cardiac, mesentery, adrenal and brain medulla DBH activity at different postoperative times will be compared with catecholamine content of tissues. Effects of adrenalectomy, indices of sympathetic activity will be studied.